Re: [dbus-cplusplus-devel] Proposal: Give objects through dbus-c++

[Andreas V. <li...@br...>]

Am Sun, 31 Aug 2008 18:16:13 +0200 schrieb P. Durante:

Hello Paolo,

currently I work on a example implementation that explains all my
ideas. I hope tomorrow it's finished and ready to show. Then we talk
again about it.

regards
Andreas

> Hi,
> 
> On Sat, Aug 30, 2008 at 12:24 AM, Andreas Volz <li...@br...>
> wrote:
> > Hello,
> >
> > while writing a DBUS interface for my application I found a way to
> > give objects direct "through" DBUS. In reality the objects aren't
> > give through DBUS. Only the copyable contents are given though DBUS.
> >
> > So how does it work?
> >
> > See the example communication framework here. It's only a prototype
> > and still has some problems.
> >
> > http://tux-style.de/tmp/oicf-0.1.tar.gz
> >
> > Look at OICFControlListener.cpp: (below as reference. Use the
> > source for more overview)
> >
> > class OICFControlListener :
> >  public org::oicf::ControlListener,
> >  public DBus::IntrospectableProxy,
> >  public DBus::ObjectProxy
> > {
> > public:
> >  OICFControlListener ( DBus::Connection& connection, const char*
> > path, const char* name ) : DBus::ObjectProxy (connection, path,
> > name) {}
> >
> >  virtual void onAxisListener (const KeyEvent &event) = 0;
> >  virtual void onButtonListener (const KeyEvent &event) = 0;
> >
> > private:
> >  void onAxisListener(const KeyEvent_Dbus_t &eventAxis)
> >  {
> >    KeyEvent event;
> >    event << eventAxis;
> >
> >    onAxisListener (event);
> >  }
> >
> >  void onButtonListener(const KeyEvent_Dbus_t &eventButton)
> >  {
> >    KeyEvent event;
> >    event << eventButton;
> >
> >    onButtonListener (event);
> >  }
> >
> > };
> >
> > As you see the private onAxisListener() from dbus-c++ is
> > overwritten and creates the object KeyEvent, fills it with the '<<'
> > operator and calls the new public callback function.
> >
> > Look into KeyEvent.h:
> 
> I've perused the archive but can't find this file
> 
> >
> > typedef ::DBus::Struct <int32_t, int16_t, uint8_t, bool>
> > KeyEvent_Dbus_t;
> >
> > class KeyEvent
> > {
> > public:
> > ...
> >
> > public:
> >  int32_t time;
> >  int16_t value;
> >  int8_t number;
> >
> > public:
> >  void operator << (const KeyEvent_Dbus_t& event)
> >  {
> >    time = event._1;
> >    value = event._2;
> >    number = event._3;
> >  }
> > };
> >
> 
> from what I've read you basically want to automate marshaling and
> unmarshaling of DBus structured types, is that correct?
> if this where to be done in the code generator, where would the field
> names (in this case, "time", "value", "number") be stored? in the xml?
> 
> > This works as long as '<<' and '>>' operator is implemented correct
> > in the class you like to give "through" dbus-c++. (See
> > CoordWGS84.h) for another example.
> >
> 
> this file can't be found either :-\
> 
> > For sure objects are not given through DBUS, but it looks and
> > behaves for the user in that way.
> >
> > Look at the introspection XML:
> >
> > <?xml version="1.0" ?>
> > <node name="/org/oicf/ControlListener">
> >  <interface name="org.oicf.ControlListener">
> >
> >    <signal name="onAxisListener">
> >      <arg type="(inyb)" name="eventAxis" direction="out"/>
> >    </signal>
> >
> >    <signal name="onButtonListener">
> >      <arg type="(inyb)" name="eventButton" direction="out"/>
> >    </signal>
> >
> >  </interface>
> >
> > </node>
> >
> > You see that it has a struct that exactly fits the KeyEvent.h data.
> >
> > This works so far, but it's much way to write all that wrapper
> > functions on my own. This is exact the work a code generator is
> > done for. I would propose to change the XML format in that way:
> >
> > <?xml version="1.0" ?>
> > <node name="/org/oicf/ControlListener">
> >  <interface name="org.oicf.ControlListener">
> >
> >    <signal name="onAxisListener">
> >      <arg type="(inyb)" name="eventAxis" direction="out"
> > object="KeyEvent"/> </signal>
> >
> >    <signal name="onButtonListener">
> >      <arg type="(inyb)" name="eventButton" direction="out"
> > object="KeyEvent"/> </signal>
> >
> >  </interface>
> >
> > </node>
> >
> >
> > So the code generator know that he should add some code to give
> > "class KeyEvent" in a "KeyEvent.h" in dbus-c++ as shown above. The
> > only thing that has to be hand written is the KeyEvent.h and the
> > '<<' and '>>' operator.
> >
> > This proposal is backwards compatible as other DBUS implementations
> > simply ignore the "object" tag and give access to the data with the
> > normal DBUS mechanisms.
> >
> 
> XML interfaces are supposed to be distributed to allow interoperation
> with other applications and/or languages, since this addition would be
> very specific to this particular implementation it could be
> implemented using a dedicated annotation, other languages and bindings
> (Glib and Qt come to mind) already do it, see
> 
> http://dbus.freedesktop.org/doc/dbus-specification.html
> 
> and look for "annotations"
> 
> > What do you think about this idea?
> >
> 
> from what I understand you basically want to implement CORBA
> ValueTypes in DBus :-)
> 
> > regards
> > Andreas
> >
> 
> regards,
> Paolo
>